Page 189 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-14 Infectious Diseases

Prevalence rates
LEPROSY (HANSEN’S DISEASE) (per 10,000 population)
0 (no cases reported)
Less than 1
Leprosy is a chronic multisystem disease with cutane- 1.0–1.5
ous findings that is caused by the bacteria, Mycobacte- 1.5–2.0
rium leprae. It also goes by the name Hansen’s disease. 2 and above
Gerhard Hansen was the Norwegian physician who No data
first described M. leprae as the cause of leprosy in 1873.
Leprosy is most prevalent in regions of Africa, South-
east Asia, and South America, and it can be seen in
isolated regions of North America.
Clinical Findings: Cutaneous findings often begin as
a solitary hypopigmented macule. The area of involve-
ment often has a loss of sensation and temperature
discrimination. This initial phase has been termed inde-
terminate leprosy. At this point, it is unknown what type
of overall immune response the host will mount. After Based on Leprosy prevalence, beginning of 2009. WHO.
a period of time, if the host’s cell-mediated immune
response is able to keep the bacteria in check, the
patient develops tuberculoid leprosy or paucibacillary
leprosy. Tuberculoid leprosy manifests with one to
three patches or plaques. The border tends to be raised,
with a central depression. Adnexal structures, such as
hair, are lost, and the lesions are often hypopigmented.
This form of leprosy tends to affect the peripheral
nerves (e.g., median nerve, ulnar nerve). Palpation of
the involved nerve demonstrates enlargement and
irregularly spaced nodules. Nerve involvement leads to
impairment of the innervated skin and muscle.
Those patients who do not mount a strong cell-
mediated immune reaction develop lepromatous
leprosy or multibacillary leprosy. Up to hundreds of
hypopigmented patches and plaques may be present.
Hair loss may occur in the affected skin and along the Multiple patches seen in
eyelashes and eyebrows. This form of leprosy can affect lepromatous leprosy; central
many nerves in a widespread region, leading to neu- healed areas tend to be
ropathy. There are varying degrees of cell-mediated Typical early pattern of sensory Patches and plaques hypesthetic or anesthetic
immune response, and the disease is classified by the loss in leprosy (Hansen disease) on face and ears (dimorphous leprosy).
Ridley-Jopling system. tends to affect cooler skin areas
Pathogenesis: M. leprae is an acid-fast mycobacterium not following either segmental or
that is found in environments where the temperature nerve distribution; area kept warm
averages approximately 29°C. Most likely, the bacte- by watchband is not affected.
rium is inhaled and subsequently invades the skin and
other tissues by hematogenous spread. This bacterium
is classified as an obligate intracellular organism. It sur-
vives within histiocytes, in which it is protected from
host defense systems. Infected individuals with a poor
immune response develop lepromatous leprosy, whereas
those with an excellent response develop tuberculoid
leprosy. Several genes are being evaluated as potential
susceptibility markers, because it appears that the
organism is not highly contagious. It is estimated that
only 5% of those exposed eventually develop disease.
This bacterium is highly unusual in that it can infect
peripheral nerves. The bacterium expresses a protein, Late-stage finger
phenolic glycolipid 1 (PGL-1), that has the ability to Biopsy specimen of nerve reveals abundant contractures with
bind to peripheral nerve cells. This allows initial entry acid-fast bacilli (M. leprae). ulcerations due to
into the host and provides the bacteria with a place to sensory loss
replicate. Many other tissue types can be infected.
Histology: The skin biopsy can be extremely helpful
in confirming or making the diagnosis of leprosy. The
biopsy findings are highly dependent on the type of
leprosy the patient develops. Biopsies of paucibacillary
leprosy show a granulomatous infiltrate with few bac- dermal infiltrate is made up of plasma cells, lympho- Treatment is based on the bacillary load. Paucibacillary
teria present. The bacteria can be sparsely located, and cytes, and foamy histiocytes. The histiocytes, when disease can be treated with a regimen of rifampin,
the tissue must be stained with a modified acid-fast stain observed under oil immersion, show numerous bacteria. minocycline, ofloxacin, and dapsone. The treatment
(Fite method) to appreciate the small, red, rod-shaped Bacteria are also seen scattered throughout the dermis. schedule varies during the course of therapy, which is 6
bacteria. These can be seen only with an oil-immersion Treatment: Guidelines for the treatment of leprosy months long, and following the protocol is extremely
objective. have been established by the World Health Organi- important. Multibacillary disease requires longer
In multibacillary leprosy, the infiltrate is a mixed zation (WHO), and one should always refer to the therapy and uses a combination of dapsone, clofazi-
dermal infiltrate with an overlying Grenz zone. The most recent information when treating this disease. mine, and rifampin.

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